1. Field of the Invention
The present invention relates generally to surgical devices, and more particularly, to a surgical device for applying radio frequency energy to a portion of a captured vessel, preferably to a side branch of a vessel to be harvested for a coronary bypass graft (CABG).
2. Prior Art
Surgeons and surgical assistants have been using medical devices incorporating radio frequency (RF) electricity for many years to cauterize and coagulate bodily tissues during surgical procedures. Two types of RF surgical devices are conventionally utilized: mono-polar and bipolar. Both incorporate a pair of conductors for transmission of alternating RF electricity. In a mono-polar electrosurgical instrument, a first conducting electrode having a first polarity is typically placed on the patient""s skin and communicates through the body, i.e. forms a conductive path, with a second conducting electrode having the opposite polarity located on the surgical instrument.
A bipolar electrosurgical instrument, however, typically incorporates both first and second electrodes of opposite polarity in the same surgical instrument, substantially restricting the flow path of electric current to tissue that is contained between the electrodes. As mentioned previously, both mono-polar and bipolar electrosurgical instruments apply RF energy through tissue. The energy is dissipated within the tissue in the form of heat due to the natural impedance of tissue. As the temperature of the tissue rises, the electrical resistivity of the tissue increases. When RF energy is applied to tissue, and as the temperature reaches about 67-70 degrees Celsius., the tissue begins to coagulate. As increasing amounts of energy dissipate in the tissue, the collagen forming the tissue matrix breaks down and appears to xe2x80x9cmeltxe2x80x9d. Mechanical compression of the coagulating tissue layers fuses and seals any contained blood vessels, so that the tissue may be cut without bleeding. When the tissue temperature reaches 100 degrees C., most fluids (including water) vaporize into the surrounding tissues and air.
The energy dissipation rate in tissue depends on numerous factors, including the inherent electrical resistivity of the tissue and the electrical current density. Electrical current density in various tissues is an important consideration in the design of the electrodes in a bipolar electrosurgical instrument, including the number, size, shape, and placement of the electrodes.
Many surgeons prefer to use bipolar electrosurgical instruments for hemostatically (without bleeding) sealing tissue prior to transection. Bipolar electrosurgical devices are known for grasping, coagulating, and cutting tissue. Typically the instruments have grasping elements, and one of the grasping elements is an electrically opposite pole of the other grasping element. For this type of conventional, bipolar electrical configuration, electrical current can be simplistically thought of as xe2x80x9cflowingxe2x80x9d from one grasping element (a positive pole), through the grasped tissue, and to the other grasping element (a negative pole).
In a coronary artery bypass graft (CABG) procedure, a surgeon or surgical assistant may remove a saphenous vein from one of the patient""s legs to use as one or more bypass grafts on that patient""s heart. In recent years, new surgical dissecting/retracting tools have been introduced to enable the surgical operator to harvest the saphenous vein endoscopically. Examples of endoscopic vessel harvesting devices and methods are contained in the following U.S. patents, which are incorporated by reference: U.S. Pat. Nos. 5,667,480; 5,722,934; 5,928,135; and 5,928,138. In such surgical procedures the operator xe2x80x9ctunnelsxe2x80x9d with the surgical dissecting/retracting tool alongside the vein under the skin, working through a small incision made into the inside of the patient""s leg or knee. The benefits of this procedure to the patient are numerous because endoscopic vein harvesting (EVH) results in greatly reduced recovery time and pain for the patient as compared to the earlier open procedure of creating an incision along the leg equal to the length of the vein harvested. In addition scarring is limited, and the incidence of serious infections reduced.
In conventional EVH procedures, the surgical operator uses the surgical dissecting/retracting tool to create a small working space at the distal end of the tool and adjacent to the vein being harvested. The tool generally has a lumen for insertion of an endoscope so that the procedure is performed under direct observation. As the operator maneuvers the tool along the vein to separate the vein from adjacent tissues, the operator typically encounters numerous smaller collateral vascular side branches of the main vein (usually about 15). To harvest the main vein with minimal bleeding of surrounding tissues, the operator may apply at least two conventional surgical clips to each side branch encountered, using a conventional mechanical endoscopic surgical clip applier. Then the clip applier is removed, an endoscopic scissors is inserted to cut the side branch between the applied clips. Each instrument insertion and removal is not only time-consuming, but care must be taken not to cause trauma to the vein being harvested and to surrounding tissues in the leg. The operator may also use bipolar electrosurgical scissors in place of mechanical clip appliers, which are well known in the art for use in this type of surgical procedure.
Therefore, surgeons must exchange instruments for ligating and transecting the side branches and must also coordinate the viewing of the image of the side branch with the manipulation of the ligation and transection instruments in order to ligate and transect the side branch.
Therefore it is an object of the present invention to provide a surgical device for applying radio frequency energy to a portion of a captured vessel to seal vessels under direct observation.
It is another object of the present invention to provide a surgical device for applying radio frequency energy to a portion of a captured vessel, which minimizes instrument exchanges.
Accordingly, a surgical device for applying radio frequency energy to a portion of a captured vessel is provided. The device comprises: a first tube having an internal lumen for passage of a viewing device therein, the first tube having a substantially transparent first window at a distal tip thereof; a second tube slidingly disposed over the first tube, the second tube having a substantially transparent second window at a distal tip thereof, the second tube further having a slot for capturing a portion of the vessel; actuation means for sliding the second tube relative to the first tube between open and closed positions, wherein in the closed position an inner surface of the second window is aligned with an outer surface of the first window and captures the portion of the vessel therebetween; and at least one electrode affixed to one of the inner or outer surfaces and facing the other of the inner or outer surfaces for applying radio frequency energy to the captured portion of the vessel. The first and second windows are preferably offset at an angle relative to an axial direction of the lumen and the slot is preferably flush and parallel with the inner surface of the second window. The captured vessel is preferably a side branch of an artery being harvested.
Preferably, the first tube comprises a proximal portion and a distal portion, wherein the distal portion including the first window is substantially transparent. More preferably, the device further comprises orientation means for maintaining the orientation of the first tube relative to the second tube such that the inner surface of the second window is aligned with the outer surface of the first window. The orientation means preferably comprises a slot on one of the first or second tubes and a corresponding key on the other of the first or second tubes such that the key is disposed in the slot to prevent relative rotation between the first and second tubes.
The actuation means preferably comprises at least one projection disposed on a proximal end of the second tube, wherein pulling the projection in a proximal direction slides the second tube relative to the first tube into the closed position and pushing the projection in a distal direction slides the second tube relative to the first tube into the open position.
The at least one electrode preferably comprises two electrodes affixed to the outer surface of the first window, each of the electrodes being of a different polarity. More preferably, the at least one electrode comprises at least two sets of electrodes affixed to the outer surface of the first window, each of the sets of electrodes having an electrode of a first polarity and an electrode of a second polarity, wherein the first and second polarities are opposite. The first window preferably further having holes, for connecting at least two electrodes of the same polarity through the holes and along an inner surface of the first window.
The device preferably further comprises flushing means for flushing at least one of the outer surface of the first window or inner surface of the second window with a liquid. The flushing means preferably comprises a conduit having a proximal end connected to a liquid source and a distal end adjacent to the first window, the distal end being configured to direct the liquid across at least one of the outer surface of the first window or the inner surface of the second window. The conduit is preferably disposed in an annular space between the first and second tubes and further comprising a spacer disposed in the annular space for maintaining a parallel relationship between the first and second tubes.
Also provided is a method for applying radio frequency energy to a portion of a captured vessel, the method comprising: providing a first tube having an internal lumen for passage of a viewing device therein, the first tube having a substantially transparent first window at a distal tip thereof and providing a second tube slidingly disposed over the first tube, the second tube having a substantially transparent second window at a distal tip thereof, the second tube further having a slot for capturing a portion of a vessel, at least one electrode being affixed to one of the inner or outer surfaces and facing the other of the inner or outer surfaces; viewing the vessel through the first and second windows; capturing a portion of the vessel in the slot; sliding the second tube relative to the first tube between open and closed positions, wherein in the closed position an inner surface of the second window is aligned with an outer surface of the first window to sandwich the portion of vessel therebetween; and applying radio frequency energy to the at least one electrode to cauterize the captured portion of vessel.
Preferably the method further comprises maintaining the orientation of the first tube relative to the second tube such that the inner surface of the second window is aligned with the outer surface of the first window.
The sliding step preferably comprises fixing the first tube relative to the endoscope and pulling a projection disposed on the second tube in a proximal direction to slide the second tube relative to the first tube into the closed position and pushing the projection in a distal direction to slide the second tube relative to the first tube into the open position. The method preferably further comprises flushing at least one of the outer surface of the first window or inner surface of the second window with liquid.